Abstract
Suspensory activity of Japanese macaques was reported in this study. Study site is the Tsubaki Wild Monkeys Park in Wakayama Prefecture in Japan. The subjects were 15 identified individuals which were provisioned. Focal sampling method was adopted. Hanging by arm (s), by leg (s) and by arm (s) and leg (s) were all observed. Hanging often attends limb rotation, limb joint extension and palmer flexion. But both forelimb (s) and hindlimb (s) hanging doesn't so much need knee or hip joint extension. Hindlimb (s) hanging goes with the wider limb rotation in younger animals. Both the frequency and duration of all suspensory activity were significantly (but inversely) correlated with age class. Hindlimb (s) hanging and both forelimb (s) and hindlimb (s) hanging were never observed in adult age class animals. But adult individuals adopted forelimbs suspension although that frequency was low. The ontogenetic change of suspensory activity may be related to the decrease in limb joint mobility as well as in relative weight of the digital flexors to body weight. The attribute of Japanese macaques suspensory activities are different from that of other primates suspensory behavior. Hanging is an important component of various positional behaviors which constitute one arboreal transferring session. All age class individuals adopted hanging when they transferred a vertical wide gap, whereas suspensory activity has never observed in feeding and horizontal transferring in adult age class individuals. Suspensory activities observed in transferring ended in short moments in Japanese macaques. But under another situation (ex. play, horizontal transferring and so on), suspensory activities were observed in younger age class and lasted rather long period.
